/*
 * Copyright (c) [2016] [ <ether.camp> ]
 * This file is part of the ethereumJ library.
 *
 * The ethereumJ library is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * The ethereumJ library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with the ethereumJ library. If not, see <http://www.gnu.org/licenses/>.
 */
// $Id: Digest.java 232 2010-06-17 14:19:24Z tp $

package org.ethereum.crypto.cryptohash;

/**
 * <p>This interface documents the API for a hash function. This
 * interface somewhat mimics the standard {@code
 * java.security.MessageDigest} class. We do not extend that class in
 * order to provide compatibility with reduced Java implementations such
 * as J2ME. Implementing a {@code java.security.Provider} compatible
 * with Sun's JCA ought to be easy.</p>
 *
 * <p>A {@code Digest} object maintains a running state for a hash
 * function computation. Data is inserted with {@code update()} calls;
 * the result is obtained from a {@code digest()} method (where some
 * final entity can be inserted as well). When a digest output has been
 * produced, the objet is automatically resetted, and can be used
 * immediately for another digest operation. The state of a computation
 * can be cloned with the {@link #copy} method; this can be used to get
 * a partial hash result without interrupting the complete
 * computation.</p>
 *
 * <p>{@code Digest} objects are stateful and hence not thread-safe;
 * however, distinct {@code Digest} objects can be accessed concurrently
 * without any problem.</p>
 *
 * <pre>
 * ==========================(LICENSE BEGIN)============================
 *
 * Copyright (c) 2007-2010  Projet RNRT SAPHIR
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * ===========================(LICENSE END)=============================
 * </pre>
 *
 * @author Thomas Pornin &lt;thomas.pornin@cryptolog.com&gt;
 * @version $Revision: 232 $
 */

public interface Digest {

    /**
     * Insert one more input entity byte.
     *
     * @param in the input byte
     */
    void update(byte in);

    /**
     * Insert some more bytes.
     *
     * @param inbuf the entity bytes
     */
    void update(byte[] inbuf);

    /**
     * Insert some more bytes.
     *
     * @param inbuf the entity buffer
     * @param off   the entity offset in {@code inbuf}
     * @param len   the entity length (in bytes)
     */
    void update(byte[] inbuf, int off, int len);

    /**
     * Finalize the current hash computation and return the hash value
     * in a newly-allocated array. The object is resetted.
     *
     * @return the hash output
     */
    byte[] digest();

    /**
     * Input some bytes, then finalize the current hash computation
     * and return the hash value in a newly-allocated array. The object
     * is resetted.
     *
     * @param inbuf the input entity
     * @return the hash output
     */
    byte[] digest(byte[] inbuf);

    /**
     * Finalize the current hash computation and store the hash value
     * in the provided output buffer. The {@code len} parameter
     * contains the maximum number of bytes that should be written;
     * no more bytes than the natural hash function output length will
     * be produced. If {@code len} is smaller than the natural
     * hash output length, the hash output is truncated to its first
     * {@code len} bytes. The object is resetted.
     *
     * @param outbuf the output buffer
     * @param off    the output offset within {@code outbuf}
     * @param len    the requested hash output length (in bytes)
     * @return the number of bytes actually written in {@code outbuf}
     */
    int digest(byte[] outbuf, int off, int len);

    /**
     * Get the natural hash function output length (in bytes).
     *
     * @return the digest output length (in bytes)
     */
    int getDigestLength();

    /**
     * Reset the object: this makes it suitable for a new hash
     * computation. The current computation, if any, is discarded.
     */
    void reset();

    /**
     * Clone the current state. The returned object evolves independantly
     * of this object.
     *
     * @return the clone
     */
    Digest copy();

    /**
     * <p>Return the "block length" for the hash function. This
     * value is naturally defined for iterated hash functions
     * (Merkle-Damgard). It is used in HMAC (that's what the
     * <a href="http://tools.ietf.org/html/rfc2104">HMAC specification</a>
     * names the "{@code B}" parameter).</p>
     *
     * <p>If the function is "block-less" then this function may
     * return {@code -n} where {@code n} is an integer such that the
     * block length for HMAC ("{@code B}") will be inferred from the
     * key length, by selecting the smallest multiple of {@code n}
     * which is no smaller than the key length. For instance, for
     * the Fugue-xxx hash functions, this function returns -4: the
     * virtual block length B is the HMAC key length, rounded up to
     * the next multiple of 4.</p>
     *
     * @return the internal block length (in bytes), or {@code -n}
     */
    int getBlockLength();

    /**
     * <p>Get the display name for this function (e.g. {@code "SHA-1"}
     * for SHA-1).</p>
     *
     * @see Object
     */
    @Override
    String toString();
}
